The present invention relates to apparatus for cutting sheet material and, more particularly, to a numerically controlled cutting apparatus suitable for cutting pattern pieces from fabric layups having a low stack height.
The use of numerically controlled cutting tools in the garment, automobile and other fabric-cutting industries is well established. Numerically controlled equipment is capable of cutting large quantities of pattern pieces from layups with as many as 150 plies of sheet material with high speed and accuracy. Cutting programs control the operation of a cutting tool, such as a reciprocating cutting blade, and cause it to translate through high or deep layups while the layups are held in a spread condition on a cutting table. Relative movement between the cutting blade and the layups can be produced by moving the cutting blade or the layup or both under program control.
U.S. Pat. No. 3,495,492 having the same assignee as the present invention discloses a prior art cutting apparatus in which the layup of sheet material is held in position on a vacuum table. The use of a vacuum holddown technique assists the cutting operation by holding each ply of sheet material in the layup in position relative to the other plies and the cutting surface over which the operation takes place so that precise correspondence between patterns cut from the top and bottom plies results. While cutting machines such as disclosed in the above-referenced patent may be used in cutting layups of different depths or heights above the supporting surface of the cutting table, they are designed to withstand the maximum loads experienced while cutting deep layups of 6 inches or more. Correspondingly, their speed and agility in cutting layups of low stack height are somewhat limited.
Accordingly, it is a general object of the present invention to disclose a cutting head for use in cutting machines that operate upon layups of low stack height. The head is constructed with low translation and polar moments of inertia to operate efficiently in low-stack-height layups in response to a simplified cutting program.